This invention relates to woodworking tools. Specifically, this invention relates to an articulated iron cap for a hand plane.
Hand planes have been used for hundreds of years to smooth the surface of wood. A hand plane works when a woodworker pushes or pulls the plane across the surface of the wood which allows the sharp blade or the plane iron to engage the wood and shear off a thin layer of wood, thereby smoothing the wood surface.
FIG. 1 shows an expanded view of a prior art hand plane. The hand plane assembly 10 has a base unit 12, in which the bottom of the base unit 12 is the sole 14. In addition, the base unit 12 has an opening in the sole 14 which is called the throat 16. Attached to the base unit 12 is at least one handle or tote 18. A device called a frog 20 extends upward from the inside of the base unit 12. The frog 20 holds the blade or cutter which is known as the iron 28. The user can turn the depth adjuster 22 which allows the iron 28 to extend farther through the throat 16. Adjustment of the iron 28 depth allows the iron 28 to engage a deeper or shallower cut in the wood being planed. The lateral adjuster 24 allows the user to adjust the iron 28 into a left or right position. This in turn, allows for deeper cuts on one side of the plane or the other. A bolt inserted near the center of the frog 20 is called the fulcrum stud 26. This stud 26 allows the iron 28 to be fastened securely to the frog 20, so as to make a secure, tight fit which holds the iron 28 in place during use.
In order for the iron 28 to be of use, it must be sharpened. The sharpened area on an iron 28 is called the bevel 29. Most prior art hand planes are designed in one of two ways. They either have the iron bevel up, or the bevel down in relation to the sole 14 of the plane. Typically planes that have a down bevel are similar to the design shown in the hand plane assembly 10. On the other hand, common bevel up irons are used in a different style of hand plane (not shown) which do not have the frog. Instead, the iron 28 lays on an inclined surface on the inside of the base unit 12 without the aid of the frog 20. This allows a bevel up iron 28 to lie at a much more reclined angle inside the base unit 12 of the plane.
A prior art bevel up type iron 28 plane which is not shown, is commonly known to one skilled in the art. A bevel up iron 28 allows a user with the much more inclined angle on the iron 28 to use the plane in more difficult types of wood. The sharper attack angle allows the plane to cut woods with more difficult grain. Thus, each type of plane, bevel up or bevel down, has its own specific purpose.
A cap iron 30 is used in conjunction with the iron 28 on bevel down type planes. The cap iron 30 is secured to the iron 28 by the use of a cap iron screw 36. This cap iron 30 acts as a chip breaker which helps to curl the cuttings cut by the iron 28 before they have a chance to split away from the larger working piece of wood. The end result is that the chip breaker part 38 on forward end of the cap iron 30 as seen in FIG. 1A, which is the rounded-out bottom portion of the cap iron, is desirable in bevel down type irons 28. Overall, the chip breaker contributes for much smoother cutting on the work surface of the wood. The iron 28 and the cap iron 30 when bolted together by the use of the cap iron screw 36 become one piece, which is held onto the frog 20 by the use of the lever cap 32. This lever cap has a lever 34 with a cam on the end which applies pressure against the cap iron 30 to hold the cap iron 30 and the iron 28 assembly in place on top of the frog 20. The cam on the bottom of the lever 34 causes the lever cap 32 to pivot around the fulcrum stud 26 and remain tight on the cap iron 30 and iron 28 assembly.
Typically, most lever caps 32 are of solid construction cast metal with the only moving part as the lever 34. This allows for a solid lever action while pivoting at the fulcrum stud 26 to allow force on the cap iron 30 to hold it tight. However, other types of lever caps 32 have been developed. For example, U.S. Pat. No. 1,822,520 discloses a clamping lever assembly 40 which is seen in FIGS. 2, 3 and 4. This clamping lever assembly 40 was comprised essentially of two main sections, the clamping lever main body 44 and the clamping lever tip 46. On the back side near the lever 34 is a spring 42 which helps to hold the lever 34 into place which maintains pressure or tension on the cap iron 30 and iron 28 assembly. The clamping lever main body 44 and the clamping lever tip 46 are held together by a rivet which is loosely fit and allows the clamping lever tip 46 to move a little with respect to the clamping lever main body 44. On the bottom of the clamping lever tip 46 are two lugs 48. These lugs also engage the cap iron 30 and iron 28 assembly to apply pressure to the assembly to hold it tight on the plane. The bearing edge 50 is what contacts the cap iron 30 to apply pressure to the iron 28 to hold it tight during operation of the plane. Here again, a fulcrum stud 26 goes through the fulcrum slot 52 to allow the assembly to mount together.
One of the problems with existing planes is that frogless planes lack a chip breaker. This can cause a “lever-effect” of a shaving and wood can be “torn” out ahead of the cut. The result is an undesirable rough cut. Another problem with this type of assembly of the prior art, is that the pressure from the lever cap 32 or the clamping lever assembly 40 is applied to the cap iron behind the cutting edge of the iron 28. This allows the cutting edge of the iron 28 to vibrate and contributes to rough cuts. This creates opportunities for vibration and flex of the iron 28. This leads to chatter in thin cuts as the iron 28 loads and depends on the user to maintain a rigorous and forceful motion to keep the iron loaded during use. Every cutting edge, whether in wood or metal, needs a load (or bite) to work properly. With hand planes, the load occurs when the cutting edge first encounters the material to be cut. The edge of the blade or iron 28 deflects slightly and as long as there is significant forward motion of the plane, the iron 28 remains loaded and cuts the material.
The primary object of the present invention is to provide an improved plane iron cap.
It is a further object of this invention to allow the iron to be tensioned or loaded while locked in place.
It is a further object of this invention to create the ability to vary the depth of the cut while the iron is locked in place.
It is a further object of this invention to add mass and tension to the area of the iron that is unsupported in traditional planes therefore making the iron more rigid.
It is a still further object of the invention to create a plane which dramatically dampens vibration during use.
It is a further object of the invention to create a cap iron which also functions as a chip breaker.
It is a further object of the invention to eliminate the need to separate the iron from the chip breaker on the cap iron prior to sharpening.
It is a still further object of the invention to create a seal between the iron and the chip breaker which eliminates tuning of new planes and prevent chips from becoming lodged between the chip breaker and the iron.
It is a still further object of the current invention to allow bevel up planes to have the aid of a chip breaker.
It is a still further object of the invention to minimize grain lift when using the plane to plane wood.
It is a further object of the invention to allow the cap iron to seat throughout the entire lateral adjustment range of the iron.
It is a further object of the invention to allow the cap to seat against the iron regardless of the primary grind angle or bevel on the iron.
It is a still further object of the invention to add mass to the cutting edge of the iron to act as a vibration dampener.
It is a still further object of the invention to create a plane which can eliminate the use of a frog while still having a chip breaker.
It is a further object to move the flexing point of the iron from the fulcrum stud down closer to the cutting edge of the iron.
A further object is the provision of the articulated plane iron cap which is economical to manufacture, durable in use, and efficient in operation.
One or more of these or other objects of the invention will be apparent from the specification and claims that follow.